A skew correction circuit for correcting skew between two signals has been known. In one example, a skew correction circuit has a phase comparator and an integration circuit and is connected to a signal generation circuit having a first signal generation circuit, a second signal generation circuit, and a delay circuit. The first signal generation circuit in the signal generation circuit generates a reference signal, and the second signal generation circuit in the signal generation circuit generates a comparison signal. The phase comparator in the skew correction circuit outputs a phase difference between the reference signal and the comparison signal, and the integration circuit in the skew correction circuit integrates a signal output from the phase comparator and outputs a signal proportional to the phase difference to the delay circuit in the signal generation circuit. Based on a delay time generated by integrating the phase difference between the reference signal and the comparison signal, the skew correction circuit delays the comparison signal generated by the second signal generation circuit to thereby correct skew between a signal generated by the first signal generation circuit and a signal generated by the second signal generation circuit.
Other known examples include a system using a multi-stage gate circuit to correct a delay time of data, a system using a flip-flop circuit, a system using a phase-locked loop circuit, and a system using a differentiation or integration circuit to perform phase correction.
Differential signals having a positive signal and a negative signal with an inverted phase of the positive signal are used during communication of information through a transmission path, such as during communication between large scale integration (LSI) circuits. During communication of differential signals from a transmitting circuit to a receiving circuit through a transmission path, skew may occur between the positive signal and the negative signal of the differential signals received by the receiving circuit, for example, owing to a difference between the length of a transmission line through which the positive signal is transmitted and the length of a transmission line through which the negative signal is transmitted. Since there is a possibility that erroneous information is communicated owing to the skew between the positive signal and the negative signal of the differential signals, it is desirable to correct the skew between the positive signal and the negative signal of the differential signals.
The followings are reference documents.    [Document 1] Japanese Laid-open Patent Publication No. 2003-110422 and    [Document 2] Japanese Laid-open Patent Publication No. 2004-207794.